Question

An aqueous solution containing 4.71 g of an optically pure compound was diluted to 400.0 mL with water and placed in a polarimeter tube 15.0 cm long. The measured rotation was -4.19℃ at 25 ℃. Calculate the specific rotation of the compound.

Answer 1

Concepts and reason

Calculate the concentration of the aqueous solution using the given values of mass and volume.

Substitute the given values of concentration, path length and measured rotation to get the value of specific rotation.

Fundamentals

Specific rotation is a property of chiral compounds. It is defined as the rotation caused by the chiral compound. It is measured at a particular temperature, wavelength and concentration. The formula for specific rotation is as follows:

Here, is the measured rotation in degrees, is the path length in decimetres, T is the temperature in degree Celsius, c is the concentration of solution and is the wavelength in nanometres

The given values for the aqueous solution are as follows:

Calculate the concentration of solution as follows:

Convert the given path length from cm to dm as follows:

The specific rotation is calculated as follows:

Therefore, the specific rotation of the given aqueous solution is .

Ans:

The specific rotation of the given aqueous solution is .